floodplains

Floodplains are the flat or gently sloping lands adjacent to rivers and streams that are periodically flooded when rivers overflow their banks. They form from the deposition of sediments carried by the river during flood events, creating fertile alluvial soils that often extend beyond the current channel. The size and shape of a floodplain are influenced by flood frequency, river channel dynamics, and vegetation.

During floods, water spreads across the floodplain, depositing sediments and nutrients and recharging groundwater. Over time, this process builds layered soils and creates landscape features such as natural levees, backswamps, channels, oxbow lakes, and wetlands. The flood regime, including the duration and frequency of inundation, strongly influences plant and animal communities and ecological succession.

Ecology and services: Floodplains support high biodiversity and productivity, providing critical habitats for fish, birds, amphibians, and invertebrates. They act as nutrient sinks, helping to improve downstream water quality, and store floodwater, reducing downstream flood peaks. Human communities also benefit from the fertile soils used for agriculture and from recreational and aesthetic values.

Human use and management: Floodplains host farms, residences, and infrastructure, which creates exposure to flood risk. Management approaches include zoning and setback planning, levees and spillways, flood forecasting, and, increasingly, river restoration to reconnect rivers with their floodplains. Restoration aims to restore natural flood regimes, wetlands, and habitat connectivity to enhance resilience and biodiversity.

Threats: Urbanization, drainage, and dams can disrupt floodplain connectivity and sediment regimes. Climate change may alter flood patterns, posing challenges for ecosystems and human infrastructure.